You can test it by clicking the little cell phone icon in the lower left under Developer tools, then select rest_command.triggercmd_calculator in the Service field, then click CALL SERVICE. This is what it should look like:

I installed Home Assistant on my QNAP nas as a Docker container. If you do that, I recommend these two settings:

Create a folder you have access to, and mount it as /config in your container. That will give you easy access to the configuration files, and when you upgrade the container, you can re-mount this folder to /config.

Use HOST networking, so you can access Home Assistant at a URL like http://nas:8123.